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Sternotherus depressus

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Taxonomy [top]

Kingdom Phylum Class Order Family
ANIMALIA CHORDATA REPTILIA TESTUDINES KINOSTERNIDAE

Scientific Name: Sternotherus depressus
Species Authority: Tinkle & Webb, 1955
Common Name(s):
English Flattened Musk Turtle

Assessment Information [top]

Red List Category & Criteria: Critically Endangered A2bce+4bce ver 3.1
Year Published: 2013
Date Assessed: 2010-08-01
Assessor(s): van Dijk, P.P.
Reviewer(s): Horne, B.D., Mittermeier, R.A., Philippen, H.-D., Quinn, H.R., Rhodin, A.G.J. & Shaffer, H.B.
Justification:
Sternotherus depressus inhabits a limited range in a single drainage system in Alabama. Its habitat has been under severe impact from pollution and sedimentation from nearby open coalmining, and impoundment of stream sections. Diseases has impacted the species and animals are in some demand for the pet trade. Surviving populations occupy about 7% of historically suitable habitat, and remain at lower abundance than 20 years previously. Generation time is unknown but likely to be over 20 years. Much of the historical impact has ceased or been brought under tighter regulation, but while the remaining populations have mostly stabilized, population recovery to pre-impact levels has not been documented. It can be argued that the species has lost about 90% of total habitat and associated populations in its past two generations, and while causes of reduction have largely ceased, they are not clearly reversible, and population recovery to historical levels is unlikely in the future two generations if present trends and processes continue. Overall the species qualifies for Critically Endangered.
History:
1996 Vulnerable
1994 Vulnerable (Groombridge 1994)
1990 Vulnerable (IUCN 1990)
1988 Vulnerable (IUCN Conservation Monitoring Centre 1988)
1986 Indeterminate (IUCN Conservation Monitoring Centre 1986)

Geographic Range [top]

Range Description:

Sternotherus depressus inhabits a small range in the Black Warrior River system of Alabama.

The area of occupancy (AOO) and extent of occurrence (EOO) have not been quantified, but the EOO is at the order of 7,000 km2 while an AOO of less than 500 linear km of streams and rivers is a realistic estimate.
Countries:
Native:
United States (Alabama)
Range Map: Click here to open the map viewer and explore range.

Population [top]

Population:

Dodd (1990) estimated that 56.3% of historically suitable habitat was degraded to the point that it had lost its S. depressus populations, 36.9% was severely degraded and contained remnant populations, and only 6.9% of original habitat remained reasonably unaffected by pollution, sedimentation and impoundments. Throughout the 1990s, populations continued to decline (Bailey and Guyer 1998), and the most recent surveys (before 2006) indicate that some viable populations remain, these were considered stable but at lower abundance than they had been in the mid-1980s (Dodd 2008).

Population Trend: Decreasing

Habitat and Ecology [top]

Habitat and Ecology:

Sternotherus depressus is a nearly exclusively aquatic freshwater turtle, inhabiting medium-sized clean clear-water streams and small rivers with abundant rocky crevice cover-sites and preferably extensive snail populations.

Flattened musk turtles feed predominantly on freshwater snails and (introduced) clams, also taking some aquatic insects and their larvae (Marion et al. 1991).

Males reach sexual maturity at four to six years, females at six to eight years of age, at about 65 mm carapace length (CL). Females reach their maximum size of 12.0 cm at 30-40 years of age, males at 50-60 years (Close and Holmes in Dodd 2008). Mature females produce an average of two clutches of one to three eggs annually. Hatchlings measure 31-33 mm CL (Dodd 2008). Generation time is unknown but estimated at estimated 20-30 years.

Systems: Terrestrial; Freshwater

Use and Trade [top]

Use and Trade: Sternotherus depressus is prohibited from trade.

Threats [top]

Major Threat(s):

Sternotherus depressus is primarily threatened by habitat degradation and loss, and secondarily by collection and possibly disease. Siltation, from coal strip mining and improper runoff and stream bank management associated with forestry, agriculture and construction, eliminates the essential rock crevice hiding areas, reduces or eliminates molluscan prey, and may contain toxic compounds.

While the species is legally protected from collection, illegal collection for pets remains a concern (Dodd 2008).

A severe disease outbreak swept through the Sipsey Fork population in 1985-1986, more than halving its population in one year; disease was also recorded at other streams but its impact was not quantified. The diseases has been speculated to involve a compromised immune system. By 1995 the Sipsey Fork population had not yet recovered to pre-disease levels (Bailey and Guyer 1998), and Fonnesbeck and Dodd (2003) documented that a short-term modest reduction in survivorship created serious long-term consequences for the population.

Leech infestation rates are inversely correlated to environmental pollution levels (Dodd 1988).

Conservation Actions [top]

Conservation Actions:

Sternotherus depressus is designated as Threatened in the US ESA since 1987, with no critical habitat designated. It is protected from exploitation and intentional impact by Alabama State legislation since 1984 (Code of Alabama, Section 9-11-269).  

Populations are confirmed from the Bankhead National Forest including the Sipsey Wilderness Area.

Surveys have documented and monitored distribution and status since the mid-1980s.

A Recovery Plan was approved by FWS in 1990 but not funded, and no actions have resulted from its ESA inclusion.

Future desirable research include further status surveys, continued population monitoring, further investigation of disease, refined demography and population dynamics studies including genetic studies to document population fragmentation effects, telemetry studies of habitat usage and movements, mollusc prey studies, contaminant studies, and further biological / natural history research.

Conservation actions proposed include local efforts to restore stream quality in the Warrior basin, and improvement and enforcement of water quality and mining laws and regulations (Dodd 2008).


Citation: van Dijk, P.P. 2013. Sternotherus depressus. The IUCN Red List of Threatened Species. Version 2014.3. <www.iucnredlist.org>. Downloaded on 20 December 2014.
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